• Journal of Microbiology and Biotechnology
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• 제16권4호
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• pp.619-622
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• 2006

Biotransformation is a good tool to synthesize regioselective compounds. It could be performed with diverse sources of genes, and microorganisms provide a myriad of gene sources for biotransformation. We were interested in modification of flavonoids, and therefore, we cloned a putative O-methyltransferase from Bacillus cereus, BcOMT-2. It has a 668-bp open reading frame that encodes a 24.6-kDa protein. In order to investigate the modification reaction mediated by BcOMT-2, it was expressed in E. coli as a His-tag fusion protein and purified to homogeneity. Several substrates such as naringenin, luteolin, kaempferol, and quercetin were tested and reaction products were analyzed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC). BcOMT-2 could transfer a methyl group to substrates that have a 3' functional hydroxyl group, such as luteolin and quercetin. Comparison of the HPLC retention time and UV spectrum of the quercetin reaction product with corresponding authentic 3'-methylated and 4'-methylated compounds showed that the methylation position was at either the 3'-hydroxyl or 4'-hydroxyl group. Thus, BcOMT-2 transfers a methyl group either to the 3'-hydroxyl or 4'-hydroxyl group of flavonoids when both hydroxyl groups are available. Among several flavonoids that contain a 3'- and 4'-hydroxyl group, fisetin was the best substrate for the BcOMT-2.

• 한국식품과학회지
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• 제31권3호
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• pp.815-822
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• 1999

우리 나라 전역에 자생하는 쑥(Artemisia vulgaris)의 전초의 수용성 에탄올추출물로 부터 21가지의 flavonoids를 분리하였다. 이들 화합물의 동정은 H-NMR, mass, UV-스펙트럼을 이용하여 동정하였으며, 동정된 flavonoids들은 tricin, jaceosidine, eupafolin, diosmetin, chrysoeriol, humoeridictyol, isorhamnetin, apigenin, eriodictyol, luteolin, luteolin 7-glucoside, kaempferol 3-glucoside, kaempferol 7-glucoside, kaempferol 3-rhamnoside, kaempferol 3-rutinoside, quercetin, quercetin 3-glucoside, quercetin 3-galactoside, quercetin, quercetin 7-glucoside, rutin 그리고 vitexin으로 동정 되었다. 이들 분리된 각 flavonoids들에 대하여 쥐의 간에서 추출한 마이크로좀에 대하여 지질과산화 효과를 살펴보았다. 이들 flavonoids화합물들의 항산화효과는 비타민 E와 비교하였을 때 높은 활성이 나타났다. 이미 강력한 항산화물질로 잘 알려진 quercetin, apigenin, eriodictyol등의 화합물의 $IC_{50}$ 값은 각각 0.9, 0.3, $0.3\;{\mu}g/mL$로 나타났으며, methoxylated flavonoids인 eupafolin, jaceosidine, diosmetin 등의 화합물도 $IC_{50}$ 값이 1.0, 1.4, $1.0\;{\mu}g/mL$로 나타나 비타민 E에 비교할 때 높은 활성을 나타냈다.

• Journal of Microbiology and Biotechnology
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• 제20권9호
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• pp.1359-1366
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• 2010

A search of the Streptomyces avermitilis genome reveals that its closest homologs are several O-methyltransferases. Among them, one gene (viz., saomt5) was cloned into the pET-15b expression vector by polymerase chain reaction using sequence-specific oligonucleotide primers. Biochemical characterization with the recombinant protein showed that SaOMT5 was S-adenosyl-L-methionine-dependent Omethyltransferase. Several compounds were tested as substrates of SaOMT5. As a result, SaOMT5 catalyzed O-methylation of flavonoids such as 6,7-dihydroxyflavone, 2',3'-dihydroxyflavone, 3',4'-dihydroxyflavone, quercetin, and 7,8-dihydroxyflavone, and phenolic compounds such as caffeic acid and caffeoyl Co-A. These reaction products were analyzed by TLC, HPLC, LC/MS, and NMR spectroscopy. In addition, SaOMT5 could convert phenolic compounds containing ortho-dihydroxy groups into O-methylated compounds, and 6,7-dihydroxyflavone was known to be the best substrate. SaOMT5 converted 6,7-dihydroxyflavone into 6-hydroxy-7-methoxyflavone and 7-hydroxy-6-methoxyflavone, and caffeic acid into ferulic acid and isoferulic acid, respectively. Moreover, SaOMT5 turned out to be a $Mg^{2+}$-dependent OMT, and the effect of $Mg^{2+}$ ion on its activity was five times greater than those of $Ca^{2+}$, $Fe^{2+}$, and $Cu^{2+}$ ions, EDTA, and metal-free medium.

• Natural Product Sciences
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• 제14권4호
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• pp.281-288
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• 2008

From the MeOH extract of the whole plants of Lathyrus davidii (Fabaceae), thirteen constituents were isolated and identified as the flavonoids astragalin, isoquercitrin, nicotiflorin, and rutin, as the saponins soyasapogenol B 3-O-${\beta}$-D-glucuronopyranoside, azukisaponins II and V, soyasaponins II and V and as 4-O-${\beta}$-Dglucopyranosyl syringic acid, uracil and n-hexacosanol. Five saponins and 4-O-${\beta}$-D-glucopyranosyl syringic acid were isolated from the BuOH fraction as their methyl esters. Ombuoside (rutin 7,4'-di-O-methyl ether) was also isolated from the methylated BuOH-soluble fraction. However, no ombuoside was detected in the HPLC analysis of the nonmethylated BuOH fraction. Therefore, ombuoside is an artifact derived from methylation of rutin. All of these compounds were isolated for the first time from this plant.